Centrifugal separator

TECHNICAL FIELD

0001The present invention relates to a centrifugal separator. The present invention also relates to an analyzer provided with a centrifugal separator.

BACKGROUND ART

0002As is well known, in addition to red cells and white cells, blood contains various components such as glucose, albumin, calcium and the like. Methods for measuring concentrations of these components include an optical method and an electrochemical method. Specifically, a sample (blood) as an analyte is applied to a pad (which is generally worked into an elongated test piece) retaining a reagent, and the resulting reaction is analyzed optically or electrochemically. In the optical method, a portion of the reagent pad which exhibits color reaction is irradiated with light, and the light reflected thereon or the light passing therethrough is analyzed. In the electrochemical method, electrochemical change during the oxidation/reduction reaction occurring in the reagent pad is analyzed with electrodes. Through such analysis, the concentration of a particular component in the blood is determined.

0003Whichever one of the optical method and the electrochemical method is utilized, to measure the concentration of a component other than blood cells (i.e. blood plasma) while avoiding measurement errors, it is preferable to separate blood plasma from blood cells in advance. Generally, for this purpose, a centrifugal separator is used.

0004Conventionally, various analyzers incorporating centrifugal separators are proposed for automatically measuring the concentration of a component in blood. An example of such analyzers is disclosed in JP-A-61 (1986)-13158. As shown in <figref idref="DRAWINGS">FIG. 11</figref> of the accompanying drawings of the present application, the disclosed analyzer (generally indicated by reference number <b>8</b>) includes a centrifugal separator <b>9</b>, a pipette unit <b>80</b>, a constant-temperature bath <b>81</b> and an optical measuring unit (not shown).

0005As shown in <figref idref="DRAWINGS">FIG. 12</figref>, the centrifugal separator <b>9</b> includes three rotary discs <b>90</b> equally spaced from each other along a hypothetical circumference. The discs <b>90</b> are fixed to a rotation shaft <b>92</b> via horizontal arms <b>92</b>. The rotation shaft <b>92</b> is rotatable about its axis intermittently at a pitch of 120 degrees. Therefore, each of the discs <b>90</b> stopped at one of three stop points A, B and C shown in <figref idref="DRAWINGS">FIG. 11</figref> moves to a next one of the points.

0006As shown in <figref idref="DRAWINGS">FIG. 12</figref>, each of the rotary discs <b>90</b> is circumferentially provided with a plurality of holes <b>93</b> equally spaced from each other. As shown in <figref idref="DRAWINGS">FIG. 13</figref>, a cylindrical container <b>95</b> for holding a test tube <b>94</b> is pivotally provided in each of the holes <b>93</b>.

0007As shown in <figref idref="DRAWINGS">FIG. 11</figref>, the analyzer <b>8</b> has an upper surface <b>82</b> formed with an opening <b>83</b> which is generally equal in diameter to the discs <b>90</b>, thereby exposing the upper surface of the disc <b>90</b> (<b>90</b><i>a</i>) positioning at the first stop point A. Therefore, the test tubes <b>94</b> (<figref idref="DRAWINGS">FIG. 12</figref>) can be easily inserted into the cylindrical containers <b>95</b> (<figref idref="DRAWINGS">FIG. 13</figref>) in the discs <b>90</b>.

0008After test tubes are inserted into all of the cylindrical containers <b>95</b> of the disc <b>90</b><i>a</i>, the rotation shaft <b>91</b> (<figref idref="DRAWINGS">FIG. 12</figref>) is rotated through 120° to move the disc <b>90</b><i>a </i>to the second stop point B. At this point, the disc <b>90</b><i>a </i>is rotated at a speed of no less than 3000 rpm to centrifugally separate the sample.

0009Subsequently, the rotation shaft <b>91</b> (<figref idref="DRAWINGS">FIG. 12</figref>) is further rotated through 120° to move the disc <b>90</b><i>a </i>to the third point C. The upper surface <b>82</b> of the analyzer <b>8</b> is formed, at the stop point C, with a pipette insertion hole <b>84</b> of a relatively small diameter. At the stop point C, an intended one of the test tubes <b>94</b> supported by the disc <b>90</b><i>a </i>can be located directly below the pipette insertion hole <b>84</b> by intermittently rotating the disc <b>90</b><i>a</i>. Thus, supernatant liquid (blood plasma) is taken from each of the test tubes <b>94</b> through the pipette insertion hole <b>84</b>.

0010The blood plasma thus taken is spotted, through a spotting hole <b>85</b>, to reagent pads of test pieces (not shown) set in the constant-temperature bath <b>81</b>. The color reaction occurring at each of the reagent pads is analyzed by the above-described optical method.

0011Although the above-described prior art analyzer <b>8</b> functions properly in many ways, it has the following problems.

0012Generally; the number of test tubes <b>94</b> to be set to the centrifugal separator <b>9</b> is not always the same but may vary at each time of the operations for centrifugal separation. Specifically, in one case, all of the cylindrical containers <b>95</b> may be loaded with test tubes <b>94</b> (containing samples), but in another case, the number of test tubes <b>94</b> to be set may be smaller than the number of cylindrical containers <b>95</b>. In the former case, the center of gravity of the three rotary discs <b>90</b> (and the test tubes <b>94</b> containing samples) coincides with the axis of the rotation shaft <b>92</b>. However, in the latter case, the center of gravity of the three rotary discs <b>90</b> (and the test tubes <b>94</b> containing samples) does not coincide with the axis of the rotation shaft <b>92</b>. Therefore, the axis deflection of the rotation shaft <b>92</b> is likely to occur during the operation, which increases the possibility of the failure of the centrifugal separator <b>9</b>.

0013Conventionally, to avoid such a trouble, measures need be taken for keeping the rotation balance of the centrifugal separator when the number of the test tubes <b>94</b> containing samples is smaller than the maximum capacity. Specifically, the test tubes <b>94</b> need be so set in each rotary disc as to be far from each other as much as possible or a dummy test tube or tubes as a counterbalance need be used.

0014However, such works are troublesome and considerably deteriorate the efficiency of the sample analysis. Particularly, in a small-scale hospital which has only one or two doctors, it is not advantageous to use the above-described analyzer <b>8</b>. This is because, generally in such a small-scale hospital, it is not usual to perform blood tests simultaneously with respect to many samples, so that the work for balancing the rotation of the centrifugal separator <b>9</b> is almost always necessary. Further, since the prior art analyzer <b>8</b> is relatively large, it maybe difficult to find appropriate space for disposing the analyzer in such a small-scale hospital.

DISCLOSURE OF THE INVENTION

0015The present invention is conceived under the circumstances described above. Therefore, an object of the present invention is to provide a compact analyzer which is capable of efficiently analyzing a single kind of sample at a time.

0016Another object of the present invention is to provide a centrifugal separator used for such an analyzer.

0017According to a first aspect of the present invention, there is provided a centrifugal separator including a driving source, a rotor and a swing member. The rotor is rotatable about a rotation axis by the driving source. The swing member is pivotally suspended by the rotor and includes an accommodation space for retaining a separation liquid analyte.

0018Preferably, the rotor has a center of gravity which is offset from the rotation axis. The center of gravity of the assembly made up of the rotor and the swing member coincides with the rotation axis when the rotor is rotated while pivoting the swing member through a predetermined angle with a predetermined amount of separation liquid analyte contained in the accommodation space.

0019Preferably, the swing member is removable from the rotor.

0020Preferably, the swing member is provided with a pair of shaft portions projecting therefrom whereas the rotor is provided with an engagement member for engagement with the shaft portions.

0021Preferably, the engagement member includes a pair of guides spaced from each other, and each of the guides includes a cutout for receiving the shaft portion and an inclined surface connected to the cutout.

0022Preferably, the swing member includes an upper opening and a bevel portion tapering toward the upper opening.

0023Preferably, the swing member includes a container defining the accommodation space and a lid attached to the container, and the upper opening is formed at the lid. The lid includes a rim which is connected to the upper opening and which has a constant diameter.

0024Preferably, the rotor is provided with a stopper for restricting the pivot angle of the swing member relative to the rotor.

0025Preferably, the swing member has a vertical axis which coincides with the rotation axis of the rotor when the rotor is not rotated.

0026Preferably, the swing member has a vertical axis which is offset from the rotation axis of the rotor when the rotor is not rotated.

0027Preferably, the rotor includes a bottom surface, and a side surface formed with a cutout.

0028Preferably, the centrifugal separator further comprises a detecting unit for detecting the number of rotations of the rotor and a determination unit for determining whether or not the center of gravity of the rotor during the rotation is offset from the rotation axis based on the data obtained by the detecting unit.

0029Preferably, the determination unit determines that the center of gravity is offset when the number of rotations of the rotor has not reached a predetermined value after lapse of a predetermined time since the rotor started to rotate.

0030Preferably, the centrifugal separator further comprises a stopping unit for stopping the rotation of the rotor when the determination unit determines that the center of gravity of the rotor during the rotation is offset.

0031According to a second aspect of the present invention, there is provided an analyzer comprising a centrifugal separator, a pipette unit, a measurement unit and a positioning mechanism. The centrifugal separator includes a rotor rotatable about a rotation axis and a separation container pivotally suspended by the rotor. The pipette unit sucks a liquid sample contained in the separation container and supplies the sucked sample onto a reagent. The measurement unit, if based on optical principles, irradiates the reagent with light and measures the reflected light or transmitted light. The positioning mechanism moves the rotor to a predetermined position after centrifugal separation is completed. A predetermined amount of liquid sample is retained in the separation container in advance. When the rotor in this state is rotated while pivoting the separation container through a predetermined, the center of gravity of the assembly made up of the rotor and the separation container coincides with the rotation axis.

0032Preferably, the positioning mechanism includes a detecting unit for detecting whether or not a positioning portion provided at the rotor in advance is deviated, rotor rotating means for rotating the rotor when the positioning portion is deviated, a driving mechanism for moving the rotor in a direction perpendicular to the rotation axis of the rotor, and a stopper member which is movable vertically in accordance with the movement of the rotor by the driving mechanism.

0033Preferably, the analyzer further comprises a slide table and a casing movable on the slide table by the driving mechanism. The rotor is held by the casing. The slide table includes a higher flat surface and a lower flat surface. The stopper member moves vertically by coming into engagement with the higher flat surface or the lower flat surface in accordance with the movement of the casing.

0034Preferably, the rotor is provided with an engagement hole. The stopper member is inserted into the engagement hole to positionally fix the rotor.

0035Preferably, the engagement hole is tapered for facilitating the insertion of the stopper member.

BRIEF DESCRIPTION OF THE DRAWINGS

0036<figref idref="DRAWINGS">FIG. 1</figref> is a perspective view illustrating an analyzer according to a first embodiment of the present invention.

0037<figref idref="DRAWINGS">FIG. 2</figref> illustrates a pipette mechanism and an optical measurement unit used for the analyzer of the first embodiment.

0038<figref idref="DRAWINGS">FIG. 3</figref> illustrates a centrifugal separator unit for use in the analyzer of the first embodiment.

0039<figref idref="DRAWINGS">FIG. 4</figref> is a perspective view illustrating a rotor for use in the centrifugal separator unit of <figref idref="DRAWINGS">FIG. 3</figref>.

0040<figref idref="DRAWINGS">FIG. 5</figref> illustrates a separation container for use in the centrifugal separator unit of <figref idref="DRAWINGS">FIG. 3</figref>.

0041<figref idref="DRAWINGS">FIG. 6</figref> illustrates the rotation of the separation container of <figref idref="DRAWINGS">FIG. 5</figref>.

0042<figref idref="DRAWINGS">FIG. 7</figref> is a sectional view illustrating an analyzer according to a second embodiment of the present invention.

0043<figref idref="DRAWINGS">FIGS. 8A–8C</figref> illustrate positional controlling of the rotor used for the analyzer of the second embodiment.

0044<figref idref="DRAWINGS">FIG. 9</figref> illustrates a stopper mechanism for use in the analyzer of the second embodiment.

0045<figref idref="DRAWINGS">FIG. 10</figref> illustrates the operation of the stopper mechanism of <figref idref="DRAWINGS">FIG. 9</figref>.

0046<figref idref="DRAWINGS">FIG. 11</figref> is a perspective view illustrating a prior art analyzer.

0047<figref idref="DRAWINGS">FIG. 12</figref> illustrates a centrifugal separator unit for use in the prior art analyzer.

0048<figref idref="DRAWINGS">FIG. 13</figref> is a sectional view taken along lines XII—XII in <figref idref="DRAWINGS">FIG. 12</figref>.

BEST MODE FOR CARRYING OUT THE INVENTION

0049Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

0050<figref idref="DRAWINGS">FIGS. 1–6</figref> illustrate a bio-sample analyzer (generally indicated by reference numeral <b>1</b>) according to a first embodiment of the present invention. The analyzer <b>1</b> functions to measure the concentration of a particular component (e.g. glucose, albumin or calcium) contained in blood. As shown in <figref idref="DRAWINGS">FIGS. 1 and 2</figref>, the analyzer <b>1</b> includes a housing <b>2</b>, a test piece mount <b>3</b>, a centrifugal separator <b>4</b>, a pipette unit <b>5</b> and an optical measurement unit <b>6</b>.

0051As shown in <figref idref="DRAWINGS">FIG. 1</figref>, the housing <b>2</b> has an upper surface provided with various kinds of operation buttons <b>2</b><i>a</i>, a display <b>2</b><i>b </i>and a discharge port <b>20</b> for a recording paper K. The operation buttons <b>2</b><i>a </i>are provided for setting measurement conditions and for controlling the operation of the analyzer <b>1</b>. The display <b>2</b><i>b </i>displays the measurements or the operation results of the operation buttons <b>2</b><i>a</i>. The recording paper K, which may be thermosensitive paper, is used for recording the measurements.

0052The housing <b>2</b> is provided, on the front side thereof, with a door <b>21</b> for opening and closing movement. When the door <b>21</b> is closed, the test piece mount <b>3</b> and the centrifugal separator <b>4</b> are housed in the housing <b>2</b>. When the door <b>21</b> is opened, the test piece mount <b>3</b> and the centrifugal separator <b>4</b> can be pulled out from the housing <b>2</b>, as shown in <figref idref="DRAWINGS">FIG. 1</figref>.

0053The test piece mount <b>3</b> is provided for disposing a test piece <b>7</b> (See <figref idref="DRAWINGS">FIG. 2</figref>). The illustrated test piece <b>7</b>, which is designed for measuring plural components, comprises a base member <b>70</b> in the form of a strip and a plurality of (five in <figref idref="DRAWINGS">FIG. 2</figref>) reagent pads <b>71</b> provided on the strip. Each of the reagent pads <b>71</b> is impregnated with a reagent which exhibits color reaction upon contacting one of the substances to be measured, such as glucose, albumin or calcium. Instead of the illustrated example, use may be made of a test piece for measurement of a single component which includes a single reagent pad on a single base member. The test piece <b>7</b> for measurement of plural components is retained in a first slit <b>30</b> of the test piece mount <b>3</b>. As shown in <figref idref="DRAWINGS">FIG. 1</figref>, the first slit <b>30</b> is elongated in a direction perpendicular to the sliding direction of the test piece mount <b>3</b>. On the other hand, the test piece for measurement of a single component is retained in one of second slits <b>31</b> (six slits illustrated in the figure) of the test piece mount <b>3</b>. Each of the second slits <b>31</b> is elongated in a direction parallel to the sliding direction of the test piece mount <b>3</b>.

0054As shown in <figref idref="DRAWINGS">FIG. 3</figref>, the centrifugal separator <b>4</b> includes a casing <b>40</b>, a rotor <b>41</b>, a cuvette <b>42</b>, a detecting unit <b>80</b>, a determination unit <b>81</b> and a stopping unit <b>82</b>. As will be described later, the cuvette <b>42</b> is removably attached to the rotor <b>41</b>.

0055The casing <b>40</b> has an upper surface formed with a through-hole <b>40</b><i>a</i>. Directly below the through-hole is arranged a DC motor M<b>1</b>. The motor M<b>1</b> has an output shaft m to which the bottom wall <b>43</b> of the rotor <b>41</b> is fixed. Therefore, when the motor M<b>1</b> is driven, the rotor <b>41</b> rotates about the axis of the output shaft m. As shown in <figref idref="DRAWINGS">FIG. 1</figref>, beside the through-hole <b>40</b><i>a</i>, a tip set unit <b>40</b><i>b </i>is provided for holding a tip T to be mounted to the pipette unit <b>5</b> (See <figref idref="DRAWINGS">FIG. 2</figref>).

0056As shown in <figref idref="DRAWINGS">FIG. 3</figref>, the casing <b>40</b> is reciprocally slidable on a slide table <b>24</b> by a known driving mechanism <b>23</b>. The driving mechanism <b>23</b> may be a rack-and-pinion actuator, for example. In this case, a pinion (not shown) is pivotally mounted to the casing <b>40</b>, whereas a rack (not shown) for meshing with the pinion is fixed to the slide table <b>24</b>. The casing <b>40</b> houses a reversely rotatable motor M<b>2</b> having a rotation shaft connected to the pinion. With this structure, when the door <b>21</b> of the housing <b>2</b> is open, it is possible to automatically pull out the centrifugal separator <b>4</b> from the housing <b>2</b> or to automatically put the centrifugal separator into the housing <b>2</b>.

0057As shown in <figref idref="DRAWINGS">FIGS. 3 and 4</figref>, the rotor <b>41</b> has a circumferential wall <b>44</b> formed with a cutout <b>44</b><i>b </i>connected to an upper opening <b>44</b><i>a</i>. The rotor is further provided with a bulging portion <b>44</b><i>c </i>on the opposite side of the cutout <b>44</b><i>b</i>. Therefore, the center of gravity of the rotor <b>41</b> is offset toward the bulging portion <b>44</b><i>c </i>by a predetermined amount. The offset amount is so set that the cuvette <b>42</b> containing a predetermined amount of blood rotates stably together with the rotor <b>41</b> about the axis of the rotor when the motor M<b>1</b> is driven at a predetermined rotation speed. Therefore, according to the illustrated embodiment, a conventionally used counterbalance is not necessary, and centrifugal separation of a sample can be performed using only a single cuvette.

0058The bulging portion <b>44</b><i>c </i>is provided with a mark <b>80</b><i>a </i>which constitutes part of the detecting unit <b>80</b>. Details of the detecting unit <b>80</b> will be described later.

0059The rotor <b>41</b> has an upper surface <b>44</b><i>d </i>provided with a positioning crown <b>45</b>. As shown in <figref idref="DRAWINGS">FIG. 4</figref>, the positioning crown <b>45</b> includes a pair of guides <b>45</b>B and a bridge <b>45</b>A. The bridge <b>45</b>A extends above the cutout <b>44</b><i>b</i>. The guides <b>45</b>B are spaced from each other with the upper opening <b>44</b><i>a </i>located therebetween. Each of the guides <b>45</b>B includes a bearing portion <b>45</b><i>a </i>and an inclined surface <b>45</b><i>b</i>. The bearing portion <b>45</b><i>a </i>is provided generally centrally of the guide <b>45</b>B. The lower end of the inclined surface <b>45</b><i>b </i>is connected to the bearing portion <b>45</b><i>a. </i>

0060The rotor <b>41</b> having the above-described structure may be formed by making an intermediate casting from aluminum and then mechanically working the intermediate casting. The weight of the rotor <b>41</b> may be about 20 grams.

0061As shown in <figref idref="DRAWINGS">FIG. 5</figref>, the cuvette <b>42</b> includes a main body <b>46</b> and a lid <b>47</b>. The main body <b>46</b> is in the form of a bottomed cylinder having an accommodation space <b>48</b><i>c </i>(See <figref idref="DRAWINGS">FIG. 6</figref>). The main body <b>46</b> has a side wall from which a pair of arms <b>48</b> extend in opposite directions from each other. Each of the arms <b>48</b> includes a shaft <b>48</b><i>a </i>and an engagement portion <b>48</b><i>b</i>. The two shafts <b>48</b><i>a </i>have a common axis Ax. Each of the shafts <b>48</b><i>a </i>has a diameter which generally coincides with the width of the bearing portions <b>45</b><i>a</i>. Each of the engagement portions <b>48</b><i>b </i>has a diameter which is larger than the width of the bearing portions <b>45</b><i>a</i>. The arms <b>48</b> are pivotally received in the bearing portions <b>45</b><i>a</i>. As a result, the cuvette <b>41</b> is pivotable about the axis Ax relative to the rotor <b>41</b>.

0062As shown in <figref idref="DRAWINGS">FIGS. 5 and 6</figref>, the lid <b>47</b> includes a central opening <b>47</b><i>a</i>, a bevel portion <b>47</b><i>b </i>and a rim <b>47</b><i>c</i>. The opening <b>47</b><i>a </i>communicates with the accommodation space <b>48</b><i>c </i>of the main body <b>46</b>. The bevel portion <b>47</b><i>b </i>is tapered toward the opening <b>47</b><i>a</i>. The rim <b>47</b><i>c </i>has a constant diameter. The lid <b>47</b> further includes an engagement portion <b>47</b><i>d </i>(See <figref idref="DRAWINGS">FIG. 6</figref>) projecting downward from the bevel portion <b>47</b><i>b</i>. By fitting the engagement portion <b>47</b><i>d </i>into the accommodation space <b>48</b><i>c </i>of the main body <b>46</b>, the lid <b>47</b> is attached to the main body <b>46</b>.

0063The main body <b>46</b> and the lid <b>47</b> are formed by molding a resin. The length from the bottom of the main body <b>46</b> to the arms <b>48</b> may be about 10–20 mm. The accommodation space <b>48</b><i>c </i>may have a volume of about 300–500μl. The blood sample contained in the main body <b>46</b> is separated into blood cells and blood plasma by the centrifugal separation, as described later. At that time, the blood cells precipitate, while the blood plasma becomes a supernatant liquid.

0064As shown in <figref idref="DRAWINGS">FIG. 2</figref>, the pipette unit <b>5</b> includes a nozzle <b>50</b> and a tip T for attachment to the nozzle. Though not illustrated, the nozzle <b>50</b> is internally provided with a thin elongate pressure generation tube for selectively generating a negative pressure to suck a sample and a positive pressure to discharge a sample. The sucked sample is retained in the space within the tip T but does not contact the nozzle <b>50</b>. In the illustrated embodiment, the pipette unit <b>5</b> takes the supernatant liquid (blood plasma) from the cuvette <b>42</b> and applies the liquid to each of the reagent pads <b>71</b> of the test piece <b>7</b>. For this purpose, the pipette unit <b>5</b> is movable vertically and horizontally.

0065As shown in <figref idref="DRAWINGS">FIG. 2</figref>, the optical measurement unit <b>6</b> includes a plurality of light emitting elements <b>60</b> and a plurality of light receiving elements <b>61</b>. Each of the light emitting elements <b>60</b> may be a light emitting diode (LED), for example. Each of the light receiving elements <b>61</b>, which may be e.g. a photoelectric conversion element, receives the light reflected by a corresponding one of the reagent pads <b>71</b>. In the figure, five reagent pads <b>71</b> as well as the same number of light emitting elements <b>60</b> and the same number of light receiving elements <b>61</b> are illustrated. Actually, however, the optical measurement unit <b>6</b> includes a larger number of light emitting elements and light receiving elements. Specifically, as described before, the test piece mount <b>6</b> can carry one test piece <b>7</b> (having five reagent pads <b>71</b>) for measurement of plural components and six test pieces (each having one reagent pad <b>71</b>) for measurement of a single component at a time. Therefore, to individually irradiate eleven (=5+1×6) reagent pads <b>71</b> with light, eleven light emitting elements <b>60</b> are provided. Accordingly, the optical measurement unit <b>6</b> includes eleven light receiving elements <b>61</b>. The light emitting elements <b>60</b> and the light receiving elements <b>61</b> are fixed in the housing <b>2</b>.

0066The detecting unit <b>80</b> includes a photosensor <b>80</b><i>b </i>and a computing section <b>80</b><i>c </i>in addition to the mark <b>80</b><i>a. </i>

0067The mark <b>80</b><i>a </i>may be of any form if only it can be irradiated with light in a manner different from the side surface of the rotor <b>41</b>. For example, the mark <b>80</b><i>a </i>may have a reflectivity which is lower or higher than that of the side surface of the rotor <b>41</b>. The mark <b>80</b><i>a </i>may be provided by applying ink or attaching a tape to the side surface of the rotor <b>41</b>. Alternatively, the mark <b>80</b><i>a </i>may be a recess or a projection formed on the side surface of the rotor <b>41</b>.

0068The photosensor <b>80</b><i>b </i>includes a light emitting element (not shown) and a light receiving element (not shown), which are housed in a single package. The photosensor <b>80</b><i>b </i>is of a light-reflective type, and the light emitting face of the light emitting element and the light receiving face of the light receiving element are oriented toward the same direction (toward the rotor <b>41</b>). As shown in <figref idref="DRAWINGS">FIG. 2</figref>, the light emitted from the light emitting element is reflected by the side surface of the rotor <b>41</b>, and the reflected light is received by the light receiving element. When the light emitted from the light emitting element becomes incident on the mark <b>80</b><i>a</i>, a relatively small (or large) amount of reflected light is detected by the light receiving element. Based on such variation of light reflection amount thus detected, the computing section <b>80</b><i>c </i>computes the number of rotations of the rotor <b>41</b>.

0069Based on the number of rotations of the rotor <b>41</b> thus computed, the determination unit <b>81</b> determines whether the balance of the center of gravity of the rotor <b>41</b> is properly maintained during the rotation. Specifically, it is determined whether the number of rotations of the rotor <b>41</b> has reached a predetermined value after a lapse of predetermined time since the rotor started to rotate. If the number of rotations of the rotor <b>41</b> has reached the predetermined value, it is determined that the rotation of the rotor <b>41</b> is normal, i.e. the cuvette <b>42</b> containing a proper amount of sample is properly set to the rotor <b>41</b>. On the other hand, if the number of rotations of the rotor <b>41</b> has not reached the predetermined value, the rotation of the rotor <b>41</b> is determined to be abnormal. In this case, it is determined that the cuvette <b>42</b> does not contain a proper amount of sample or the cuvette <b>42</b> is not set to the rotor <b>41</b>.

0070When the balance of the center of gravity of the rotating rotor <b>41</b> is determined to be improper, the stopping unit <b>82</b> stops the voltage application to the rotor <b>41</b>, thereby stopping the rotation of the rotor <b>41</b>. In this way, when the cuvette <b>42</b> is not properly set to the rotor <b>41</b>, the operation of the centrifugal separator <b>4</b> is automatically stopped.

0071The computing section <b>80</b><i>c</i>, the determination unit <b>81</b> and the stopping unit <b>82</b> may comprise a CPU, a ROM, a RAM and the like for example.

0072Next, description will be made as to the usage and operation of the analyzer <b>1</b> having the above-described structure.

0073To measure the concentration of a particular component in blood other than blood cells (i.e. glucose, albumin, calcium or the like), the centrifugal separation of blood cells need be performed in the analyzer <b>1</b>. For this purpose, blood (e.g. 250μm) is injected into the cuvette <b>42</b>. Then, the cuvette <b>42</b> is set to the rotor <b>41</b> and the motor M is driven. As a result, the cuvette <b>42</b> rotates together with the rotor <b>41</b> at high speed (e.g. 14000 rpm) to separate blood cells and blood plasma.

0074When the cuvette <b>42</b> has a length of 10–20 mm and an internal volume of 400–500μl, the rotation (14000 rpm) of the cuvette <b>42</b> exerts a centrifugal force of about 1000 G onto the gas/liquid interface in the container while exerting a centrifugal force of no less than 2000 G onto the bottom of the cuvette <b>42</b>. To properly separate blood cells from blood plasma under such condition, the cuvette <b>42</b> need be rotated for 10±5 minutes, for example.

0075As shown in <figref idref="DRAWINGS">FIG. 1</figref>, the cuvette <b>42</b> is set to the rotor <b>41</b> in the state where the centrifugal separator <b>4</b> is pulled out from the housing <b>2</b> after opening the door <b>21</b> of the housing <b>2</b>. Such a state can be provided automatically by pressing a predetermined one of the operation buttons <b>2</b><i>a </i>after opening the door <b>21</b>. In this state, the main body <b>46</b> of the cuvette <b>42</b> is inserted into the opening <b>44</b><i>a </i>of the rotor <b>41</b>, and the shafts <b>48</b><i>a </i>of the cuvette <b>42</b> are brought into engagement with the bearing portions <b>45</b><i>a </i>of the positioning crown <b>45</b>. This operation can be performed easily by sliding the shafts <b>48</b><i>a </i>along the inclined surfaces <b>45</b><i>b </i>(See <figref idref="DRAWINGS">FIG. 4</figref>) of the positioning crown <b>45</b>.

0076As shown in <figref idref="DRAWINGS">FIG. 5</figref>, in the non-driven state, the cuvette <b>42</b> is suspended by the rotor <b>41</b>. At that time, the axis of the cuvette <b>42</b> generally coincides with the rotation axis of the rotor <b>41</b> (See <figref idref="DRAWINGS">FIG. 2</figref>). As shown in <figref idref="DRAWINGS">FIGS. 3 and 5</figref>, when the rotor <b>41</b> is rotated, the cuvette <b>42</b> pivots about the axis Ax of the shafts <b>48</b><i>a </i>due to the centrifugal force. At that time, if no obstacles exist, the cuvette <b>42</b> pivots through more than 90 degrees at the maximum. In practice, however, the bridge <b>45</b>A of the positioning crown <b>45</b> of the rotor <b>41</b> restricts the pivotal movement of the cuvette <b>42</b>. Thus, in the illustrated embodiment, the cuvette <b>42</b> continues to rotate together with the rotor <b>41</b> while keeping the pivot angle of about 80–85 degrees.

0077The rotation of the cuvette <b>42</b> generates airflow along the profile of the lid <b>47</b>. If no countermeasure is taken, it is probable that the airflow enters the cuvette <b>42</b> through the opening <b>47</b><i>a</i>. If the airflow enters the cuvette <b>42</b>, turbulent flow is generated in the cuvette <b>42</b> to reduce the air pressure near the opening <b>47</b><i>a</i>. Such a state unduly promotes the evaporation of the liquid component contained in the cuvette <b>42</b> and is therefore undesirable.

0078According to the illustrated embodiment, however, such a problem is effectively prevented. As described before, the lid <b>47</b> includes the bevel portion <b>47</b><i>b </i>tapered toward the opening <b>47</b><i>a </i>and the rim <b>47</b><i>c </i>having a constant diameter. Therefore, the airflow generated around the outer surface of the lid <b>47</b> travels along the path indicated by an arrow F in <figref idref="DRAWINGS">FIG. 6</figref>. That is, the airflow progresses to be farther from the opening <b>47</b><i>a</i>. Therefore, such turbulent flow as described above is not generated in the cuvette <b>42</b>, so that excessive evaporation of the liquid component in the cuvette <b>42</b> can be prevented without the need for closing the opening <b>47</b><i>a. </i>

0079After the centrifugal separation of the sample is completed, the concentration of a particular component is measured automatically. The process for automatic concentration measurement basically includes applying of the supernatant liquid (blood plasma) to a reagent pad <b>71</b>, optical detection of the color reaction on the reagent pad and computation of the detection result.

0080Specifically, blood plasma is applied to a reagent pad <b>71</b> in the following manner. Firstly, the tip T is attached to the nozzle <b>50</b> of the pipette unit <b>5</b>. The tip T to be attached is in advance set to the tip set unit <b>40</b><i>b </i>(See <figref idref="DRAWINGS">FIG. 1</figref>) provided at the casing <b>40</b> of the centrifugal separator <b>4</b>. The nozzle <b>50</b> is positioned above the set tip T and then moved downward. In this way, the tip T is automatically attached to the nozzle <b>50</b>. After the tip T is attached, the test piece <b>7</b> as shown in <figref idref="DRAWINGS">FIG. 2</figref> is disposed on the test piece mount <b>3</b>, and the test piece mount <b>3</b> is housed in the housing <b>2</b>. Subsequently, as shown in <figref idref="DRAWINGS">FIG. 2</figref>, blood plasma is sucked from the cuvette <b>42</b> by using the pipette unit <b>5</b> and applied to one of the reagent pads <b>71</b> on the test piece <b>7</b>. Specifically, the pipette unit <b>5</b> is first moved above the cuvette <b>42</b> suspended by the rotor <b>41</b>. Then, the pipette unit <b>5</b> is moved downward to dip the lower end of the tip T into the blood plasma contained in the cuvette <b>42</b>. In this state, the air pressure in the nozzle <b>50</b> is reduced to generate a negative pressure in the tip T, thereby sucking the blood plasma. The pressure drop in the nozzle <b>50</b> may be performed by driving an external pump (not shown) connected to the nozzle <b>50</b>. The sucked blood plasma is retained in the tip T. Then, the blood plasma is discharged. Specifically, first, the pipette unit <b>5</b> is moved above a desired reagent pad <b>71</b>. Then, the air pressure in the nozzle <b>50</b> is increased using the external pump to discharge the taken blood plasma onto the reagent pad <b>71</b>.

0081The above-described process of sucking and discharging blood plasma is repetitively performed for each of the reagent pads <b>71</b> of the test piece <b>7</b>.

0082Subsequently, the color reaction on the reagent pads is detected. Specifically, each of the reagent pads <b>71</b> is impregnated with a reagent which appropriately exhibits color reaction in accordance with the concentration of a particular component in the blood plasma. As described before, light emitted from the light emitting elements <b>60</b> (<figref idref="DRAWINGS">FIG. 2</figref>) is directed to the respective reagent pads <b>71</b> exhibiting color reaction, and the light reflected thereon is received by the respective receiving elements <b>61</b> individually. When the light receiving elements comprise photoelectric conversion elements, electric charge corresponding to the received amount of light (i.e. corresponding to the degree of color reaction) is generated at each of the light receiving elements <b>61</b>. The electric charge is transmitted to a computing section <b>62</b>.

0083Based on the electric charge supplied in this way, computation of the detection results is performed. The computing section <b>62</b> may comprise a CPU, a ROM, a RAM and the like, for example. The computing section <b>62</b> executes programs stored in the ROM to determine the concentration of a particular component based on the amount of light received by the light receiving element <b>61</b>. Specifically, a calibration curve (function) which correlates a received amount of light with the concentration of a particular component is generated in advance. The concentration of a particular component is determined based on the calibration curve.

0084The result of computation conducted at the computing section <b>62</b> is displayed at a display <b>2</b><i>b</i>. Further, the computation result is recorded at a recording section <b>63</b> on a recording medium such as a recording paper K or a magnetic card automatically or when the user pressed the predetermined operation button <b>2</b><i>a. </i>

0085Next, with reference to <figref idref="DRAWINGS">FIGS. 7–10</figref>, description will be made as to an analyzer (generally indicated by reference numeral <b>1</b>′) according to a second embodiment of the present invention. In these figures, the elements or portions which are identical or similar to those of the analyzer described with reference to <figref idref="DRAWINGS">FIGS. 1–6</figref> are designated by the same reference signs as those used for the analyzer, and the description of such elements will be omitted.

0086The analyzer <b>1</b>′ of the second embodiment differs from the analyzer <b>1</b> of the first embodiment in structure of a slide table <b>24</b>′ and a centrifugal separator <b>4</b>′ and in controlling mechanism of a rotor <b>41</b>′.

0087As shown in <figref idref="DRAWINGS">FIG. 9</figref>, the slide table <b>24</b>′ is provided with a pair of guide rails <b>24</b>A′. As shown in <figref idref="DRAWINGS">FIGS. 7 and 10</figref>, each of the guide rails <b>24</b>A′ include two flat surfaces <b>24</b><i>a</i>′ and <b>24</b><i>b</i>′ which differ from each other in height, and an inclined surface <b>24</b>C′ connecting the flat surfaces.

0088As shown in <figref idref="DRAWINGS">FIGS. 8A–8C</figref>, the rotor <b>41</b>′ has a side surface <b>44</b><i>e</i>′ provided with a mark <b>44</b><i>f</i>′ formed of a material having high light absorptivity or high light scattering ability. The side surface <b>44</b><i>e</i>′ is further provided with an engagement hole <b>43</b><i>a</i>′ which widens as it extends downward. The rotor <b>41</b>′ is connected to a DC motor M<b>1</b>. In the second embodiment, controlling means (not shown) is provided to intermittently supply DC current (voltage) to the DC motor M<b>1</b>. Therefore, as shown in <figref idref="DRAWINGS">FIGS. 8A and 8B</figref>, the rotor <b>41</b>′ can turn intermittently by a predetermined angle θ.

0089The rotor <b>41</b>′ suspend a cuvette <b>42</b>. When the rotor <b>41</b>′ is not rotated, the axis of the cuvette <b>42</b> is offset from the rotation axis of the rotor <b>41</b>′ by a predetermined distance (See <figref idref="DRAWINGS">FIG. 8A</figref>). With such a structure, a predetermined centrifugal force can be exerted to the blood in the cuvette <b>42</b> during the rotation of the rotor <b>41</b>′ more easily as compared with the case where the axis of the cuvette <b>42</b> coincides with the rotation axis of the rotor <b>41</b>′. Therefore, the centrifugal separation of blood can be performed properly even when the rotor <b>41</b>′ is rotated at a relatively low speed. Since the rotation speed can be decreased, the driving voltage can also be decreased, which leads to a reduction in the running cost.

0090As described above, the axis of the cuvette <b>42</b> is offset from the rotation axis of the rotor <b>41</b>′. With such a structure, if no countermeasure is taken, the cuvette <b>42</b> may stop at different positions every time when the centrifugal separation is completed. In such a case, the sucking of blood plasma with the pipette unit <b>5</b> (See <figref idref="DRAWINGS">FIG. 2</figref>) may not be performed properly.

0091To avoid such a problem, the centrifugal separator <b>4</b>′ of the second embodiment is provided with a positioning mechanism <b>72</b>′ for making the cuvette <b>42</b> stop at the same position every time when the centrifugal separation is completed. The positioning mechanism <b>72</b>′ includes detecting unit <b>73</b>′ and a stopper member <b>74</b>′.

0092As shown in FIGS. <b>7</b> and <b>8</b>A–<b>8</b>C, the detecting unit <b>73</b>′ includes a light emitting element <b>73</b>A′ and a light receiving element <b>73</b>B′. The light emitting element <b>73</b>A′ may comprise an LED, whereas the light receiving element <b>73</b>B′ may comprise a photoelectric conversion element. The light emitting element <b>73</b>A′ and the light receiving element <b>73</b>B′ are mounted on a substrate <b>73</b>C′ in facing relationship to a side surface <b>44</b><i>e</i>′ of the rotor <b>41</b>′. The substrate <b>73</b>C′ is fixed to the casing <b>40</b>′. The light emitting element <b>73</b>A′ irradiates the side surface <b>44</b><i>e</i>′ of the rotor <b>41</b>′ with light, whereas the light receiving element <b>73</b>B′ receives the light reflected by the side surface <b>44</b><i>e</i>′. When the light emitted from the light emitting element <b>73</b>A′ is incident on the mark <b>44</b><i>f</i>′, the light is absorbed or scattered at the mark <b>44</b><i>f</i>′, so that the amount of light received by the light receiving element <b>73</b>B′ decreases. The light receiving element <b>73</b>B′ outputs signals of a level corresponding to the received amount of light and transmits the signals to information processing means (not shown). Thus, the information processing means determines that the mark <b>44</b><i>f</i>′ has passed in front of the detecting unit <b>73</b>′ or that the mark <b>44</b><i>f</i>′ is positioned in front of the detecting unit <b>73</b>′.

0093As will be easily understood, the detecting unit <b>73</b>′ can be used not only for detecting the rotational position of the rotor <b>41</b>′ but also for counting the number of rotations of the rotor. Such a structure is advantageous in terms of a cost, because two different kinds of physical values can be measured by a single detecting unit.

0094As clearly shown in <figref idref="DRAWINGS">FIGS. 7</figref>, <b>9</b> and <b>10</b>, the stopper member <b>74</b>′ includes a support portion <b>74</b>A′. The support portion <b>74</b>′ has a lower portion rotatably supporting a pair of rotary members <b>74</b>B′ and an upper portion to which a pin <b>74</b>C′ is fixed.

0095As shown in <figref idref="DRAWINGS">FIG. 7</figref>, the support portion <b>74</b>A′ extends through a through-hole <b>49</b><i>a</i>′ provided in a bottom wall <b>49</b>′ of the casing <b>40</b>′ to partially project outward from the casing <b>40</b>′.

0096Each of the rotary members <b>74</b>B′ is rotatable for movement along the flat surfaces <b>24</b><i>a</i>′, <b>24</b><i>b</i>′ and the inclined surface <b>24</b><i>c</i>′ of the guide rail <b>24</b>A′.

0097The pin <b>74</b>C′ extends through a through-hole <b>74</b><i>a</i>′ of a guide fin <b>75</b>′ fixed in the casing <b>40</b>′. Between the guide fin <b>75</b>′ and the support portion <b>74</b>A′ is arranged a coil spring <b>76</b>′. Thus, the support portion <b>74</b>A′ is biased downward (toward the slide table <b>24</b>′) to keep the rotary members <b>74</b>B′ in contact with the guide rails <b>24</b>A′.

0098With the above-described structure, when the casing <b>40</b>′ moves, the rotary members <b>74</b>B′ move together with the casing <b>40</b>′ in engagement with the guide rails <b>24</b>A′. During the movement, the pin <b>74</b>C′ moves upward or downward in accordance with the partial height variation of the guide rails <b>24</b>A′. For example, when the stopper member <b>74</b>′ moves from right to left of <figref idref="DRAWINGS">FIG. 10</figref>, the pin <b>74</b>C′ moves upward as the rotary members <b>74</b>B′ ascends the inclined surfaces <b>24</b><i>c</i>′. When the stopper member moves in the opposite direction, the pin <b>74</b>C′ moves downward as the rotary members descend the inclined surfaces <b>24</b><i>c</i>′. In this way, the pin <b>74</b>C′ (i.e. the stopper member <b>74</b>′) is vertically movable in accordance with the movement of the casing <b>40</b>′. As shown in <figref idref="DRAWINGS">FIG. 7</figref>, the upper end of the pin <b>74</b>C′ is lower than the bottom surface of the rotor <b>41</b>′ when the rotary members <b>74</b>B′ are located on the lower flat surfaces <b>24</b><i>b</i>′. On the other hand, the upper end of the pin <b>74</b>C′ is higher than the bottom surface of the rotor <b>41</b>′ when the rotary members <b>74</b>B′ are located on the higher flat surfaces <b>24</b><i>a′. </i>

0099As shown in <figref idref="DRAWINGS">FIG. 7</figref>, the engagement hole <b>43</b><i>a</i>′ is so provided that its axis generally coincides with that of the pin <b>74</b>C′ when the mark <b>44</b><i>f</i>′ faces a counterpart surface <b>73</b><i>c</i>′ of the substrate <b>73</b>C′. Therefore, when the pin <b>74</b>C′ is moved upward in a state where the axis of the pin <b>74</b>C′ generally coincides with that of the engagement hole <b>43</b><i>a</i>′, the tip end of the pin <b>74</b>C′ is inserted into the engagement hole <b>43</b><i>a</i>′, as shown in <figref idref="DRAWINGS">FIGS. 7 and 9</figref>. Thus, the rotor <b>41</b>′ is locked. Since the engagement hole <b>43</b><i>a</i>′ widens as it extends downward, the insertion of the pin <b>74</b>C′ into the engagement hole <b>43</b><i>a</i>′ can be performed reliably.

0100With the positioning mechanism <b>72</b>′, the rotor <b>41</b>′ is positioned so that the mark <b>44</b><i>f</i>′ faces the substrate <b>73</b>C′ after the centrifugal separation is completed. The details are as follows.

0101First, as shown in <figref idref="DRAWINGS">FIGS. 7 and 8A</figref>, light emitted from the light emitting element <b>73</b>A′ is directed to the side surface <b>44</b><i>e</i>′ of the rotor <b>41</b>′ and the reflected light is received by the light receiving element <b>73</b>B′. At that time, when the mark <b>44</b><i>f</i>′ does not face the substrate <b>73</b>C′, pulse voltage is supplied to the DC motor M<b>1</b> to turn the rotor <b>41</b>′ only through the angle θ, as shown in <figref idref="DRAWINGS">FIGS. 7 and 8B</figref>. The pulse width (pulse duration) may be about 20–30 msec, for example, and the rotor <b>41</b>′ may be turned through about 10 degrees, for example.

0102After the rotor <b>41</b>′ is turned, the side surface <b>44</b><i>e</i>′ of the rotor <b>41</b>′ is again irradiated with light emitted from the light emitting element <b>73</b>A′ and the reflected light is received by the light receiving element <b>73</b>B′. At that time, when the mark <b>44</b><i>f</i>′ faces the substrate <b>73</b>C′ as shown in <figref idref="DRAWINGS">FIG. 8C</figref>, the driving of the rotor <b>41</b>′ by pulse voltage is finished. On the other hand, when the mark <b>44</b><i>f</i>′ does not face the substrate <b>73</b>C′, pulse voltage is supplied to the DC motor M<b>1</b> to further turn the rotor <b>41</b>′ only through the angle θ in a manner similar to the above and as shown in <figref idref="DRAWINGS">FIGS. 7 and 8B</figref>. Such pulse driving is repeated until the mark <b>44</b><i>f</i>′ faces the center of the substrate <b>73</b>C′.

0103The irradiation by the light emitting element <b>73</b>A′ and the detection of the reflected light by the light receiving element <b>73</b>B′ may be performed continuously or intermittently until the rotor <b>41</b>′ is properly positioned.

0104After the mark <b>44</b><i>f</i>′ is made to face the substrate <b>73</b>C′, the rotor <b>41</b>′ is locked by the stopper member <b>74</b>′ to keep the facing relation. The locking of the rotor <b>41</b>′ is performed by moving the casing <b>40</b>′ from right to left of <figref idref="DRAWINGS">FIGS. 7 and 10</figref>. The movement of the casing <b>40</b>′ is performed by the driving mechanism <b>23</b> (See <figref idref="DRAWINGS">FIG. 7</figref>).

0105After the rotor <b>41</b>′ and the cuvette <b>42</b> retained by the rotor <b>41</b>′ are positioned properly, the supernatant liquid in the cuvette <b>42</b> is taken by using the pipette unit <b>5</b> and applied to a reagent pad <b>71</b> of the test piece <b>7</b>, and the degree of color reaction on the reagent pad <b>71</b> is detected by the optical measurement unit <b>6</b>, as described with reference to <figref idref="DRAWINGS">FIG. 2</figref>. In this way, the concentration of a particular component can be measured.

0106The present invention being thus described, it is apparent that the same may be varied in many ways. Such variations should not be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to those skilled in the art are intended to be included within the scope of the following claims.